NullpointerException 在 Canvas 上绘制 Bitmap

Question

Why do i get a NullpointerException?

Thank you!

ps: I am new to Java.

    try {
        URL uri = new URL("http://static.panoramio.com/photos/original/41455707.jpg");
            URLConnection connection = uri.openConnection();
            Log.i(TAG, "connecting...");
            connection.connect();
            InputStream is = connection.getInputStream();
            BufferedInputStream bis = new BufferedInputStream(is, 8 * 1024);
            Bitmap bmp = BitmapFactory.decodeStream(bis);
            bis.close();
            is.close();

            Log.i(TAG, "setting bitmap");
            //Log.d(TAG, canvas.toString());
            //Log.d(TAG, bmp.toString());
            canvas.setBitmap(bmp);
    } catch (Exception exc){
        Log.e(TAG, exc.toString());
        return;
    }

the output:

06-28 17:29:04.857   391   397 I MyWallpaperPainting: connecting...
06-28 17:29:07.248   391   397 I MyWallpaperPainting: setting bitmap
06-28 17:29:07.248   391   397 E MyWallpaperPainting: java.lang.NullPointerException

Answer 1

This may be silly but did you initialize canvas somewhere previously?

Answer 2

I'm thinking you did not initialize the canvas object.

Answer 3

is that one in the overriden onDraw (Canvas canvas) method?

Answer 4

InputStream is an abstract class, i dont think you can create an instance of it, have you tried:

BufferedInputStream bis = new BufferedInputStream( new InputStream(connection.getInputStream()), 8 * 1024);

Answer 5

I'm not that good in game development, but why aren't you extending from SurfaceView and implementing Surface.CallBack and use inner AsyncTask class for handling threads? Does the job nicely! =]